The minimal spin Hamiltonian of $\alpha$-RuCl3

Determine the exchange constants of alpha-RuCl3 in $H = \sum$ over nearest-neighbor bonds $\langle ij\rangle$ of type $\gamma$ of [$J S_i . S_j + K S^{\gamma}_{i} S^{\gamma}_{j} + \Gamma (S^{\alpha}_{i} S^{\beta}_{j} + S^{\beta}_{i} S^{\alpha}_{j}) + \Gamma'$ (terms mixing $\gamma$ with $\alpha$ and $\beta$)] $+ J3 \sum$ over third neighbors of $S_i . S_j$, with $(\alpha, \beta, \gamma)$ a permutation of $(x, y, z)$, from a joint fit of inelastic neutron spectra, THz and ESR modes, the field-angle dependence of the critical field and the high-field magnon spectrum. An answer is one parameter set with error bars consistent with all these data, including the sign of $K$ and the ratio $K/\Gamma$.

A global fit of neutron, THz, ESR, magnetization and magnetostriction data using quantum many-body (beyond linear spin-wave) calculations of the spectra that yields a unique parameter set.